Basically, at lower LAN speed, LAN cable used wire point 1,2,3,6 and pin 4,5 is for telephone signal. But not for higher LAN speed.
Another thing to watch out is telephone signal carry 48v voltage. If wired in correctly, it can damage your device. So in general, not recommend to use telephone and LAN on the same wire/socket.
In my case the ISP contractor had disconnect the telephone point cable from the main telephone lines so no telephone signal at all.
That's to connect between point A to B where A is at the db (tel point) and B at the bedroom tel point, independently.
He had did on 2 bedroom telephone points and combined into 1 for in my bedroom for both internet & IPTV to run separately.
As he had mentioned that the telephone cable is using Cat-6.
Luckily the other bedroom telephone point is on the same position of the wall.
This is due to my renovation contractor foul up the data points, unable to use.